Project Summary/Abstract We are requesting funds to upgrade an existing stand-alone Bruker E-580 FT Q-band pulse EPR spectrometer. The upgrade will significantly improve signal-to-noise and allow us to carry out pulse experiments that are not presently possible using our current instrument configuration. In particular, this instrument upgrade will facilitate measurements on difficult membrane protein samples and it will improve measurements of outer-membrane proteins in whole cells and intact native membrane systems. The upgrade will allow us to carry out experiments at lower protein concentrations and obtain data on proteins that aggregate at optimal concentrations for our present EPR system. The ability to perform pulse shaping and selective excitation as well as carry out more sophisticated pulse experiments will allow us to extend the range of our measurements and improve the accuracy of longer range distance components. The components to be purchased for this upgrade include a high-power 150 Watt Q-band amplifier, a large access Q-band dielectric resonator and a cryogen-free cryostat. This upgraded instrument will serve four major users and three minor users at the University of Virginia in the Departments of Chemistry (Arts and Sciences) and Molecular Physiology (School of Medicine).